Pleiotropy does not facilitate local adaptation in the silverleaf sunflower Helianthus argophyllus

In this study, we explored connections between pleiotropy and local adaptation in the Texas endemic Silverleaf sunflower or Helianthus argophyllus. Populations of H. argophyllus exhibit a bimodal life history strategy consisting of tall, late-flowering forms and short early-flowering forms occurring in close geographical proximity. We suspect that the differential expression of life history traits within H. argophyllus populations might be linked to local adaptation and controlled by highly pleiotropic genes. We identified spatial selection, selective sweeps, and tested for local adaptation signatures. We assessed pleiotropy by examining if genes bearing adaptive mutations were more likely than expected to occupy central positions on gene coexpression networks. Our results show that candidate locally adapted genes showed significantly lower connectivity than non-adapted genes.

---

Genetic diversity and population structure

Admixture analysis using NGSAdmix suggests a population stratification into two distinct genetic groups at K = 2 representing the two sampled populations (Fig. 1B), with differences between the populations remaining at higher K values.